Luged framesets, bonding, materials, durability, questions and thoughts?

Triathlon Forum
1

I’m looking at the Colorado cyclist and they have a bike on sale, the Titus Modena, $900 frame and fork. Take away $240 for the fork and it’s $660 for a nice frame. It’s carbon tubes and aluminum lugs. I think Trek had success with this formula some years ago. Although I heard of some joint separation issues, I don’t know if it was fact or rumor.

Anyway, that leads to my question. How developed are the bonding agents between different materials in this type application.? I’m saying ‘bonding agent’ because I don’t want to sound stupid and just say ‘glue.’ Actually I don’t know the correct technical term.

A bike is subject to a lot of repetitive stresses, wide temperate variations, water and solvents, crashes, all kinds of stuff. Will these joints hold up? What materials are more easily joined?

You see I specifically opted for an all titanium frame even though I had the option to go with carbon for some tubes because I didn’t like the idea of joining the two materials. So, in the words of the ‘white angle’ “is it safe?”

And if it is safe then why can’t I just order the parts and make my own? Assuming I could rent or build a jig to hold it in perfect alignment while it sets up. Then I can order all the sizes and shapes and types of tubes I want. Maybe I want a really thick wall carbon for my chainstays, a thinner S-bend carbon for my seatstays. I’ll put lighter carbon on the seat tube and double butted aluminum on the top and down tubes. I could order them precut or cut them myself. Outside diameters would have to be standard to the lugs I suppose. I could tell the lug maker the length tubes I’m using and the effective angle I want to end up with on the bike, he plugs it into the CAD and it cuts me a set of lugs. I could event get some very ornate art work etched in for a few bucks more. I get it all in the mail, go to home depot for some glue and make myself a bike on Saturday morning.

Well, why not? I know people who build their own computers this way. It’s just a bike!

2

Pretty sure that Airbus has been putting together it jets with glue for years now rather than old-skool rivets… Doesn’t seem to be giving them any problems…

My Blue T12 is a mix of aluminum and carbon bonded together and it’s been a dream to race in the 12 duathlons I’ve done so far this year. I’ve got nothing but good things to say about it.

3

but what about 12 years from now? or even just 4? i’m very confident my all ti seven will be doing just fine. do you feel the same about your blue 12?

4

No reason why you couldn’t do that. The glues are very strong but alu-carbon joins can be subject to galvanic corrosion so you need to put fibreglass over the alu before gluing on the carbon, THis is not required for carbon-ti joins (which is why the really top end carbon frames have ti bb and headset inserts).

Talking with a mastbuilder friend he said that when a carbon-carbon joint fails it is more often a “first ply failure” - the glue is holding the layers so strongly that the first layer of carbon rips away from the 2nd. Bonding of anything works best when it is same materials.

If you like the idea of sticking together your own frame, go to bikelugs.com and look at the columbus meccano tubeset - all that requires is some good cutting tools (and lots of care) and a straight jig.

here is a site you may find interesting

http://www.signature.fi/cf.htm

as for alu lugged carbon bikes, I sold a 12yr old giant cadex last year that had served me well.

5

I dont think I would want to buy any frameset after it had been down a luge course…

http://www.usaluge.org/TeamInfo/PhotoGallery.html

Kevin

6

Why are you more confident in the 7 than a glued frame? As you allude to for glue you need the proper materials, the proper glue, a clean surface and a jig.

To weld thinwall Ti you need much more skill.

Styrrell

7

yeah, ti is great (i want one).

seriously though, how many people (especially on st) will have the same bike in 12 years, or even 4. I think I average about 3 years before I switch (due to bike lust - i haven’t had any quality issues)?

8

Why are you more confident in the 7 than a glued frame? As you allude to for glue you need the proper materials, the proper glue, a clean surface and a jig.

To weld thinwall Ti you need much more skill.

Styrrell
i think i’m more confident in the welded frame because they are the same materials bonded together. there will be no chemical reactions. with the other you have at least 3 different things: the CF, the Al and the glue all laid up together. i don’t know what’s gonna be happening to them over the years. again, i don’t know if something bad will happen, i just don’t know what will happen. i’m much more confident in a welded joint.

10

hold on, i probably didn’t present my question in the best way. i was trying to inquire about the glueing a frame together with tubes and lugs, and why can’t this be done at home to custom make a bike inexpensively. secondary to that was using different materials. i mention that because what brought the thought to mind was the picture i described of the bike that had Al lugs and carbon tubes. one might just want to use different tubes, availability might be better, shaping might be easier or cheaper… a lot of reasons to use different materials but not that it would alway be a better bike or the best possible bike.

it seemed to me Al lugs would be cheaper than carbon lugs. isn’t that why they have them on budget bikes?

11

And if it is safe then why can’t I just order the parts and make my own? Assuming I could rent or build a jig to hold it in perfect alignment while it sets up. Then I can order all the sizes and shapes and types of tubes I want. Maybe I want a really thick wall carbon for my chainstays, a thinner S-bend carbon for my seatstays. I’ll put lighter carbon on the seat tube and double butted aluminum on the top and down tubes. I could order them precut or cut them myself. Outside diameters would have to be standard to the lugs I suppose. I could tell the lug maker the length tubes I’m using and the effective angle I want to end up with on the bike, he plugs it into the CAD and it cuts me a set of lugs. I could event get some very ornate art work etched in for a few bucks more. I get it all in the mail, go to home depot for some glue and make myself a bike on Saturday morning.

Well, why not? I know people who build their own computers this way. It’s just a bike!

You certainly can make your own - go for it! A friend of mine made a carbon mountainbike frame, even going so far as to hand make the tubes and lugs. There are one or two sites out there that have advice about how to do this, which I might be able to find if requested. Arguably it’s easier to home-build a carbon frame than a welded steel frame. The Al/carbon bonding question is somewhat difficult, but it appears to have been solved very well in general bike manufacture, given how most carbon frames have aluminium drop outs and BB threads bonded into them. Mostly bonds falling apart seem to be a thing of the past. I’m not sure how the manufacturers solve the issue of the oxide layer on the aluminium; or perhaps it’s not an issue? If anyone knows the answer to this I’d be interested.

As for temperature fluxes and differences in the coefficients of thermal expansions (CTEs), for a bike frame I doubt that’s really a problem. As a little side story, I went to a talk by one of the chief materials engineers of Airbus, who took us through the different materials technologies on the new A380. IIRC some of the panels on this are laminar aluminium/carbon composites. Someone asked him if there were any problems with the different CTEs and temperature changes with these. The answer (a rough paraphrase) - we don’t really understand what’s going on but it seems to work!

12

thanks, i wish i had the time to build one. maybe some day…

i don’t know if i want to fly in a plane when the engineer says "we don’t really understand what’s going on but it seems to work! " but i suppose i probably already do !!

13

two part answer… I have a '92 Specialized Carbon Epic. There were some problems with the earlier versions where the c/f touched the aluminum and corroded. Mine is still intact and is being upgraded.

In the aerospace industry the same problems apply: Aluminum touching carbon and water getting into the carbon fiber composite. These c/f composites absorb a surprising amount of water. This becomes a problem when the moisture bridges a gap and allows electron flow between the c/f and a metal, or water condenses in a void and freezes creating delamination, or is subject to a lightning strike (haven’t heard about any bike strikes but a V-22 Osprey sized commuter aircraft takes about one a year) which instantly vaporizes the water and blows the laminate apart.

I think the water freezing in voids and the electrolysis are bicycle problems.

14

Building your own carbon frameset, while not easy by any means, is much, much, much easier than building a steel frame in the garage. I have built a few frames (no pics, as these are top-secret prototypes, all for the day that cool TT bikes come back into fashion) over the last few years.

Maclean Composites (the supplier of tubes for some of the best and brightest of U.S. bike manufacturers) makes a tubeset that is, while not economical, it takes the guesswork of trying and make your own monocoque. You will need to make your own lugs.

I would not suggest using aluminium lugs. Why do that when you could make your own carbon lugs? You could even “tack” your tubes together with glue (not stuff you get at Home Depot, more on that later), then wrap with carbon tape.

Aluminium and carbon are bad bedfellows as far as bonding is concerned. When an electrolytic element (sweat, Gatorade, etc.) is introduced, galvanic corrosion will occur, unless there is a glass insulating layer, whether it is fibre glass flock (very down layers of fibreglass), woven fabric (one layer is sufficient), or glass microballoons between the carbon and aluminium. Giant made a boat load of carbon-tubed, alu-lugged frames with mixed success. Many of these frames suffered horrible fates. Once Giant learnt what to do, then these frames did great.

Fixture jigs are only as accurate as they are set up. That being said, a carbon frame can be laid-up, glued, or however with reasonably priced fixtures made of wood. These can be re-used as you won’t be burning them with a torch. Provided you cover your working surfaces with plastic, you won’t have glue and resin screwing up your work surfaces for your next frame. Building frames can be quite addictive…

Anyhoo. You can mitre tubes with a dremel tool with sanding drums. You will need a good respirator (i.e. what painters use), as well as goggles, good, heavy gloves, and preferrably a Tyvek suit and foot covers. DP-460 by 3M is the preferred glue, and it is really, really fucking expensive, and has a very short shelf-life.

You can use pre-preg by making an oven in your garage. You can make one with foam insulation or cinder blocks and lightbulbs. You can vacuum bag with a vacuum bagging kit (available from http://www.acp-composites.com/acp-cat.htm) or compact parts with electrical tape, even though it looks lumpy.

By the time you buy all of the parts to build a frame (including fixtures and enough material to build frames to test), you probably could have bought that Titus. I don’t suggest building a fork yourself. I have built a few handlebars myself, but only after building, testing to failure, building again, testing, rebuilding- you get the idea. I have built some very stiff handlebars, but they would make most of the slowtwitch forum weight weenies say “That’s waaaaaay to fucking heavy to be cool, though it looks cool” after reading the weights (one model weighs a portly 1750 grams- stem, basebar, extensions, with some cool details that I will leave out), but they will stand up to a nuclear war.

I would suggest building and testing to failure any new design of your own in testing jigs before even testing it with a fork in the jig, let alone building it for the road.

15

Ah, but you are mistaken. Welds can fail due to dissimilar materials also. In the case of the weld it is from a contaminated weld, or from improper welding rod. This type of failure is especially common with failed Ti joints, due to the fact that oxygen is a major contaminant for Ti.

Basically any material can be built correctly or incorrectly. Chose a builder you trust with a good warrantee just in case.

Styrrell